Printing. through the interstices of a perforated pattern, as in the manufacturing of some kinds of paper hangings, he uses a cylinder entirely covered with hair or bristles in the manner of a brush.

Fig. 3.

Fig. 4.

3dly, The impressions, even in letter press printing, are performed by the action of a cylinder or cylindrical surface. The following is the construction of this machine. Fig. 3. represents a printing-press, more especially applicable to the printing of books. A and E are two cylinders, running or turning in a strong frame of wood, or metal, or both. The cylinder A is faced with woollen cloth, and is capable of being pressed with more or less force upon HI, by means of the lever M. HI is a long table, which is capable of moving endwise, backwards and forwards, upon the rollers E and K. The roller A acts upon this table by means of a cog-wheel, or by straps, so as to draw it backwards and forwards by the motion of its handle L. The table is kept in the same line by grooves on its sides, which contain the cylinder A. Ď is a chess, containing letter set up and imposed. B is a box, containing a colouring-roller, with its distributing-rollers CC; it is supported by the arm N. O is a cylinder faced with leather, and lying across an ink-block; this cylinder is fixed by the middle to a bended lever moveable on the joint Q.

The action. When D, or the letter, is drawn beneath the cylinder B, it receives ink; and when it has passed into the position R, a workman places or turns down a tympan with paper upon it (this tympan differs in no respect from the usual one, except that its hinge opens sidewise); it then proceeds to pass under the cylinder A, which presses it successively through its whole surface. On the other side, at S, the workman takes off the paper and leaves the tympan up. This motion causes the cylinder B to revolve continually, and consequently renders its inked surface very uniform, by the action of its distributing-rollers CC; and, when the table has passed to its extreme distance in the direction now spoken of, the arm G touches the lever P, and raises the cylinder O off the ink-block, by which means it dabs against one of the distributing-rollers, and gives it a small quantity of ink. The returning motion of the table carries the letter again under the roller B, which again inks it, and the process of printing another sheet goes on as before.

Fig. 4. is another printing-press. In this, B is the inking-roller; A is a cylinder, having the letter imposed upon its surface; and E is a cylinder, having its uniform surface covered with woollen cloth: these three cylinders are connected, either by cogs or straps at the edges of each. The machine is uniformly turned in one direction by the handle L. The workman applies a sheet of paper to the surface of E, where it is retained, either by points in the usual manner, or by the apparatus to be described in treating of fig. 4. The paper passes between E and A, and receives an impression; after which the workman takes it off, and applies another sheet; and in the mean time the letter on the surface of A passes round against the surface of B, and receives ink during the rotation of B. The distributing-rollers CC do their office as in the machine fig. 1.; and once in every revolution the tail F, affixed to B, raises the ink ing-piece G, so as to cause it to touch one of the distributing-rollers, and supply it with ink. In this way therefore the repeated printing of sheet after sheet goes on. VOL. XVII. Part I.

+

Fig. 5. is a printing-press, more particularly adapted Printing. to print cottons, silks, paper-hangings, or other articles which run of a considerable length. A is a cylinder Fig. 5. covered with woollen cloth, or other soft substance. The web or piece of cotton, or other goods, is passed round this cylinder, from the carrying-roller F to the receivingrollers GH; which are connected by a piece of linen, woollen, or hair-cloth, in the manner of a jack-towel, sewed round them; the rotation of this towel carries away the printed stuff or goods, and deposits them at I. KL is a moveable box, containing three rollers, which move against each other in rotation. The lowest roller C revolves in a mass of colour, contained in a trough or vessel in the bottom part of the box KL; the surface of this colour is represented by the line MN. The next roller B is stuffed and covered as described in section 2. The pressure of B against C prevents the cylinder B from receiving too much colour. D is a cut or carved cylinder, which receives colour, during the rotation, from the roller B, and impresses it upon the web as it passes round the cylinder A; in this way the constant and effectual action of the machine is sufficiently obvious. It must be observed, that the cylinders ADB and G are connected together by cog-wheels, straps, or other well-known equivalent contrivances; so that the handle P drives the whole, without their necessarily depending on any adhesion or friction at their surfaces. The pressure of B against D is governed by an adjustment of the axis of D, whose sockets are capable of a small motion; and the pressure of D against A is governed by the position of the whole box KL. When it is required to print more than one colour upon the same piece, it must pass two or more times through the machine; or, in those cases where the materials are liable to change their dimensions, it is necessary to apply, at one and the same time, two or more such boxes as KL, with their respective cylinders, so that the pattern cylinder of each may make its impression upon the web or material to be printed on.

Fig. 6. is a printing-press, chiefly of use for books and Fig. 6. papers. 1, 2, 3, 4, represent a long table, with ledges on each side; so that the two cylinders A and B can run backwards and forwards without any side shake. In one of these ledges is placed a strip or plate of metal cut into teeth, which lock into correspondent teeth in each cylinder; by which means the two cylinders roll along, without the possibility of changing the relative positions of their surfaces at any determinate part of the table. This may also be effected by straps, and may indeed be accomplished with tolerable accuracy, by the mere rolling of the cylinders on the smooth or flat ledges without any provision. A is the printing-cylinder, covered with woollen cloth, and B is the inking-cylinder, with its distributing-rollers. The table may be divided into four compartments marked with a thicker bounding line than the rest and numbered 1, 2, 3, 4. At 1 is placed a sheet of paper; at 2 is the form or chess, containing letter set and imposed; at 3 is an apparatus for receiving the printed sheet; and 4 is employed in no other use than as a place of standing for the carriage E, after it has passed through one operation, and when it takes ink at F. Its action is as follows: the carriage is thrust forward by the workman, and as the roller A passes over the space numbered 1, it takes up the sheet of paper previously laid there, while the roller B runs over the form and inks the letter. The sheet of paper being wrapped 3 B round

restore its original position at B, the pin g will return Printing. back to G. Now the figures 7 and 8 exhibit an apparatus of this kind, applied to the cylinder A; and that cylinder, by rolling over the pins P and p, properly fixed in the table to re-act upon the apparatus, will cause its prominent part G either to apply to the cylinder and clasp the paper, or to rise up and let it go. The compartment numbered 3 (fig. 6.) must of course have an apparatus of the same kind to be acted upon by pins from A, in order that it may take the paper from that cylinder.

Printing. round the cylinder A, is pressed against the form as that cylinder proceeds, and consequently it receives an impression. When A arrives at the space numbered 3, it lets go the sheet of paper, while the prominent part of the carriage G strikes the lever P, and raises the inkingpiece, which applies itself against one of the distributing rollers. In this manner therefore the cylinder A returns empty, and the cylinder B inked, and in the mean time the workman places another sheet of paper ready in the space numbered 1. Thus it is that the operation proceeds in the printing of one sheet after another.

The preceding description is not encumbered with an account of the apparatus by which the paper is taken up and laid down. This may be done in several Fig. 11, 12, ways: Fig. 11. and 12. represent one of the methods. DE is a lever, moving on the centre pin C, and having its end D pressed upwards by the action of the spring G. The shoulder which contains the pin C is fixed in another piece F, which is inserted in a groove in the surface of the cylinder A (fig. 6.), so that it is capable of moving in and out, in a direction parallel to the axis of that cylinder. As that cylinder proceeds, it meets a pin in the table; which (letter P, fig. 11.) acting on the inclined plane at the other end of the lever, throws the whole inwards, in the position represented in fig. 12.; in which case the extremity D shoots inwards, and applies itself against the side of the cylinder.

Fig. 13.

Fig. 7, 8, 9.

In fig. 13. is a representation of part of the table; the dotted square represents a sheet of paper, and the four small shaded squares denote holes in the board, with pins standing beside them. When the lever DE (fig. 12.) shoots forward, it is situated in one of these boles, and advances under the edge of the paper, which consequently it presses and retains against the cylinder with its extremity D. Nothing more remains to be said respecting the taking up, but that the cylinder is provided with two pair of these clasps or levers, which are so fixed as to correspond with four holes represented in fig. 13. It will be easy to understand how the paper is deposited in the compartment N° 3. (fig. 6.). A pin P (fig. 12.) rising out of the platform or table, acts against a pin E, projecting sidewise out of the lever, and must of course draw the slider and its lever to the original position; the paper consequently will be let go, and its disengagement is rendered certain by an apparatus fixed in the compartment numbered 3 (fig. 6.) of exactly the same kind as that upon the cylinder, and which, by the action of a pin duly placed in the surface of the cylinder A, takes the paper from the cylinder in precisely the same manner as that cylinder originally took it up in the compartment numbered 1 (fig. 6.).

Fig. 7, 8, and 9, represent a simpler apparatus for accomplishing the same purpose. If A a B b (fig. 9.) be supposed to represent a thick plate of metal of a circular form, with two pins, A and B, proceeding sidewise or perpendicularly out of its plane, and diametrically opposite to each other, and G another pin proceeding in the direction of that plane, then it is obvious that any force applied to the pin A, so as to press it into the position a (by turning the plate on its axis or centre X), will at the same time cause the pin G to acquire the position g; and, on the other hand, when B is at b, or the dotted representation of the side-pin, if any pressure be applied to

There is one other circumstance belonging to this machine which remains to be explained. When the carriage E (fig. 6) goes out in the direction of the numbers 1, 2, 3, 4, both rollers, A and B, press the form of letter in their passage; but in their return back again the roller A, having no paper upon it, would itself become soiled, by taking a faint impression from the letter, if it were not prevented from touching it the manner of effecting this may be understood from fig. 14. The apparatus there represented is fixed upon Fig. 14, the outside of the carriage E, near the lower corner, in the vicinity of the roller A; the whole of this projects sidewise beyond the ledge of the table, except the small truck or wheel B. The irregularly-triangular piece, which is shaded by the stroke of the pen, carries this wheel, and also a catch moveable on the axis or pin E. The whole piece is moveable on the pin A, which connects it to the carriage. CD, or the part which is shaded by dotting, is a detent, which serves to hold the piece down in a certain position. It may be observed, that both the detent and the triangular piece are furnished each with a claw, which holds in one direction, but trips or yields in the other, like the jacks of a harpsichord, or resembling certain pieces used in clock and watch making, as is clearly represented in the figure. These claws overhang the side of the table, and their effect is as follows: There is a pin C (fig. 6.) between the compartments of the table numbered 2 and 3, but which is marked F in fig. 14. where GH represents the table. In the outward run of the carriage these claws strike that pin, but with no other effect than that they yield for an instant, and as instantly resume their original position by the action of their respective slender back springs. When the carriage returns, the claw of the detent indeed strikes the pin, but with as little effect as before, because its derangement is instantly removed by the action of the back spring of the detent itself; but, when the claw of the triangular piece takes the pin, the whole piece is made to revolve on its axis or pin A, the wheel B is forced down, so as to lift that end of the carriage, and the detent, catching on the piece at C, prevents the former position from being recovered. The consequence of this is, that the carriage runs upon the truck B (and its corresponding truck on the opposite side) instead of the cylinder A, which is too much raised to take the letter, and soil itself; bot as soon as the end of the carriage has passed clear of the letter, another pin R (fig. 6.) takes the claw of the detent, and draws it off the triangular piece; at which instant the cylinder A subsides to its usual place, and performs its functions as before. This last pin R does not affect the claw of the triangular piece, because it is placed too low; and the claw of the detent is made the longest, on purpose that it may strike this pin.

Fig. 10. represents an instrument for printing floorcloths, paper-hangings, and the like, with a stiff paint and a brush. D is a copper or metallic cylinder fixed in a frame A, like a garden-roller; its carved part is thin, and is cut through in various places, according to the desired pattern. A strong axis passes through the cylinder, and its extremities are firmly attached to the frame A. To this axis is fixed a vessel or box of the same kind, and answering the same purpose as the box KL in fig. 5. It carries a cylinder P, which revolves in the colour; another cylinder E, which revolves in contact with P; and a third cylinder B, whose exterior surface is covered with hair, after the manner of a brush, and revolves in contact with E. This cylinder B is adjusted by its axis, in such a manner that its brush-part sweeps in the perforated parts of the metallic cylinder D. The circle C represents a cog-wheel fixed concentric to the cylinder D, and revolving with it; this wheel takes another wheel concentric to, and fixed to, B; hence the action is as follows: When the metallic cylinder is wheeled or rolled along any surface, its cogwheel C drives the brush B in the contrary direction; and this brush cylinder, being connected by cogs or otherwise with E and P, causes these also to revolve and supply it with colour. As the successive openings of the cylinder D, therefore, come in contact with the ground, the several parts of the brush will traverse the uncovered part of that ground, and paint the pattern upon it. The wheel G, being kept lightly on the ground, serves to determine the line of contact, that it shall be the part opposite to B, and no other.

Chinese PRINTING, is performed from wooden planks or blocks, cut like those used in printing of callico, paper, cards, &c.

Rolling-press PRINTING, is employed in taking off prints or impressions from copperplates engraven,etched, or scraped, as in mezzotintos. See ENGRAVING.

This art is said to have been as ancient as the year 1540, and to owe its origin to Finiguerra, a Florentine goldsmith, who, pouring some melted brimstone on an engraven plate, found the exact impression of the engraving left in the cold brimstone, marked with black taken out of the strokes by the liquid sulphur: upon this he attempted to do the same on silver plates with wet paper, by rolling it smoothly with a roller; and this succeeded: but this art was not used in England till the reign of King James I. when it was brought from Antwerp by Speed. The form of the rolling-press, the composition of the ink used therein, and the manner of applying both in taking off prints, are as follows:

The rolling-press AL, fig. 15. may be divided into two parts, the body and carriage: the body consists of two wooden cheeks PP, placed perpendicularly on a stand or foot LM, which sustains the whole press. From the foot likewise are four other perpendicular pieces, c, c, c, c, joined by other cross or horizontal ones, d, d, d, which serve to sustain a smooth even plank or table HIK, about four feet and a half long, two feet and a half broad, and an inch and a half thick. Into the cheeks go two wooden cylinders or rollers, DE, FG, about six inches in diameter, borne up at each end by the cheeks, whose ends, which are lessened to about two inches diameter, and called trunnions, turn in the cheeks about two pieces of wood in form of halfmoons, lined with polished iron to facilitate the mo

Prints.

tion. Lastly, To one of the trunnions of the upper rol- Printing, ler is fastened a cross, consisting of two levers AB, or pieces of wood, traversing each other, the arms of which cross serve instead of the bar or handle of the letter-press, by turning the upper roller, and when the plank is between the two rollers, giving the same motion to the under one, by drawing the plank forward and backward.

The ink used for copperplates, is a composition made of the stones of peaches and apricots, the bones of sheep and ivory, all well burnt, and called Frankfort black, mixed with nut-oil that has been well boiled, and ground together on a marble, after the same manner as painters do their colours.

The method of printing from copperplates is as follows: They take a small quantity of this ink on a rubber made of linen-rags, strongly bound about each other, and therewith smear the whole face of the plate as it lies on a grate over a charcoal fire. The plate being sufficiently inked, they first wipe it over with a foul rag, then with the palm of their left hand, and then with that of the right; and to dry the hand and forward the wiping, they rub it from time to time in whiting. In wiping the plate perfectly clean, yet without taking the ink out of the engraving, the address of the workman consists. The plate thus prepared, is laid on the plank of the press; over the plate is laid the paper, first well moistened, to receive the impression; and over the paper two or three folds of flannel. Things thus disposed, the arms of the cross are pulled, and by that means the plate with its furniture passed through between the rollers, which pinching very strongly, yet equally, press the moistened paper into the strokes of the engraving, whence it licks out the ink.

PRINTS, the impression taken from a copperplate. See the last article, and ENGRAVING.

From the facility of being multiplied, prints have de- Strutt's rived an advantage over paintings by no means inconsi- Dict of derable. They are found to be more durable; which Engravers, may, however, in some degree be attributed to the different methods in which they are preserved. Many of the best paintings of the early masters have generally had the misfortune to be either painted on walls, or deposited in large and unfrequented, and consequently damp and destructive buildings; whilst a print, passing, at distant intervals, from the porte feuille of one collector to that of another, is preserved without any great exertion of its owner: And hence it happens, that whilst the pictures of Raphael have mouldered from their walls or deserted the canvas, the prints of his friend and cotemporary Mark Antonio Raimondi continue in full perfection to this day, and give us a lively idea of the beauties of these paintings, which, without their assistance, had been lost to us for ever; or at least, could have been only known to us, like those of Zeuxis and Apelles, by the descriptions which former writers on these subjects have left us.

Independent of the advantages which prints affords us, when considered as accurate representations of paintings, and imitations of superior productions, they are no less valuable for their positive merit, as immediate representations of nature. For it must be recollected, that the art of engraving has not always been confined to the copying of other productions, but has frequent

3 B 2

ly

ly itself aspired to originality, and has, in this light, produced more instances of its excellence than in the other. Albert Durer, Goltzius, and Rembrandt, amongst the Dutch and Germans; Parmigiano and Della Bella amongst the Italians, and Callot amongst the French, have published many prints, the subjects of which, there is great reason to suppose, were never painted. These prints may therefore be considered as original pictures of those masters, deficient only in those particulars in which a print must necessarily be inferior to a painting.

The preceding distinction may perhaps throw some light on the proper method of arranging and classing a collection of prints, which has been a matter of no small difficulty. As an art imitating another, the principal should take the lead, and the design, composition, and drawing, in a print, being previous requisites, to the manner of execution and finishing; prints engraved after paintings should be arranged under the name of the painter; and every person who looks upon engraving only as auxilary to painting, will consequently adopt this mode of arrangement. But when engraving is considered as an original art, as imitating nature without the intervention of other methods, then it will certainly be proper to regulate the arrangement according to the names of the engravers.

PRINTS, method of cleaning. The following method of cleaning prints, is recommended as safe and effica

cious.

"Provide a certain quantity of the common muriatic acid, for example three ounces, in a glass bottle, with a ground stopper, of such a capacity that it may be only half full. Half an ounce of minium must then be added; immediately after which the stopper is to be put in, and the bottle set in a cold and dark place. The heat, which soon becomes perceptible, shews the beginning of the new combination. The minium abandons the greatest part of its oxygen with which the fluid remains impregnated, at the same time that it aequires a fine golden yellow, and emits the detestable smell of oxygenated muriatic acid. It contains a small portion of muriate of lead; but this is not at all noxious in the subsequent process. It is also necessary to be observed, that the bottle must be strong, and the stopper not too firmly fixed, otherwise the active elastic vapour might burst it. The method of using this prepared acid is as follows:

"Provide a sufficiently large plate of glass, upon which one or more prints may be separately spread out. Near the edges let there be raised a border of soft white wax half an inch high, adhering well to the glass and flat at top. In this kind of trough the print is to be placed in a bath of fresh urine, or water containing a small quantity of ox-gall, and kept in this situation for three or four hours. The fluid is then to be decanted off, and pure warm water poured on, which must be changed every three or four hours until it passes limpid and clear. The impurities are sometimes of a resinous nature, and resist the action of pure water. When this is the case, the washed print must be left to dry, and alcohol is then to be poured on and left for a time. After the print is thus cleaned, and all the moisture drained off, the muriatic acid prepared with minium is to be poured on in sufficient quantity to cover the print; immediately after which another plate of glass is

to be laid in contact with the rim of wax, in order to Print, prevent the inconvenient exhalation of the oxygenated Prior. acid. In this situation the yellowest print will be seen to recover its original whiteness in a very short time. One or two hours are sufficient to produce the desired effect; but the print will receive no injury if it be left in the acid for a whole night. Nothing more is necessary to complete the work, than to decant off the remaining acid, and wash away every trace of acidity, by repeated effusions of pure water. The print being then left to dry (in the sun if possible) will be found white, clear, firm, and in no respect damaged, either in the texture of the paper, or the tone and appearance of the impression."

It is farther recommended to those who shall adopt the whole process for clearing prints, to make the first trial with a print of little value, and in this way he will discover what portion of water should be employed in diluting the acid to prevent the corrosive action of the latter on the paper. Nichol. Journ. ii. 265. 4to.

PRIOR, in general, something before or nearer the beginning than another, to which it is compared. PRIOR, more particularly denotes the superior of a convent of monks, or the next under the abbot. See ABBOT.

Priors are either claustral or conventual. Conventual are the same as abbots. Claustral prior, is he who governs the religious of an abbey or priory in commendam, having his jurisdiction wholly from the abbot.

Grand PRIOR, is the superior of a large abbey, where several superiors are required.

PRIOR, Matthew, an eminent English poet, was born at London in 1664. His father dying while he was very young, an uncle, a vintner, having given him some education at Westminster school, took him home in order to breed him up to his trade. However, at his leisure hours he prosecuted his study of the classics and particularly of his favourite Horace. This introduced him to some polite company who frequented his uncle's house; among whom the earl of Dorset took particular notice of him, and procured him to be sent to St John's college in Cambridge, where, in 1686, he took the degree of A. B. and afterwards became fellow of that college. Upon the revolution, Mr Prior was brought to court by the earl of Dorset; and in 1690 he was made secretary to the earl of Berkeley, plenipotentiary at the Hague; as he was afterward to the ambassador and plenipotentiaries at the treaty of Ryswick in 1697; and the year following to the earl of Portland, ambassador to the court of France. He was in 1697 made secretary of state for Ireland: and in 1700 was appointed one of the lords commissioners of trade and plantations. In 1710, he was supposed to have had a share in writing The Examiner. In 1711, he was made one of the commissioners of the customs; and was sent minister plenipotentiary to France, for the negotiating a peace with that kingdom. Soon after the accession of George I. to the throne in 1714, he presented a memorial to the court of France, requiring the demolishing of the canal and new works at Mardyke. The year following he was recalled; and upon his arrival was taken up by a warrant from the house of commons, and strictly examined by a committee of the privy-council. Robert Walpole, Esq. moved the house of commons for an impeachment against him; and Mr Prior was ordered